Lipids present in blood are incorporated into the structure of lipoprotein, except for free fatty acid bound with albumin, and they are present in the form of a chylomicron (CHM), a very low density lipoprotein (VLDL), a low density lipoprotein (LDL), a high density lipoprotein (HDL), and the like. Cholesterol is particularly distributed in VLDL, LDL, and HDL. It has been known that a high level of LDL which acts to transport cholesterol, promotes arteriosclerosis. It has been known that the measurement of the level of low density lipoprotein cholesterol (LDL-C) in blood is useful for an indicator for the development and progression of arteriosclerosis.
International Publication WO00/17388 describes a method for quantifying LDL cholesterol in a biological sample, which is characterized in that, in (a) a biological sample, (b) cholesterol esterase and cholesterol oxidase or cholesterol dehydrogenase (herein referred to as CH enzymes), and (c) a low density lipoprotein (hereinafter referred to as LDL), a reaction of cholesterol is carried out in the presence of a reagent for allowing the CH enzymes described in (b) above to act on only cholesterol in the low density lipoprotein (herein referred to as LDL cholesterol), and the generated hydrogen peroxide or reduced coenzyme is then measured, so as to quantify the concentration of the LDL cholesterol. In International Publication WO00/17388, a polyoxyethylene-polyoxypropylene copolymer and a polyoxyethylene derivative are used as LDL selective reagents. However, even by quantifying LDL-C according to the method described in International Publication WO00/17388, there may be a case in which the selectivity for LDL-C is insufficient. In addition, polyoxyethylene alkyl aryl ether, which is used as a polyoxyethylene derivative in International Publication WO00/17388, unfavorably contains a compound that may cause environmental hormone risk.
JP Patent Publication (Kokai) No. 63-109799 (1988) A describes a dry analytical element, which comprises at least one water-permeable layer and a porous liquid spreading layer in a state in which the layers may be allowed to come into contact with a liquid, wherein the dry analytical element further comprises an enzyme having cholesterol ester hydrolyzing activity in the above-described spreading layer and alkyl phenoxy polyglycidol in the above-described spreading layer or the above-described at least one water-permeable layer. The polyglycidol described in JP Patent Publication (Kokai) No. 63-109799 (1988) is used to improve coating property. The dry analytical element described in JP Patent Publication (Kokai) No. 63-109799 (1988) does not have the selectivity for low density lipoprotein cholesterol (LDL-C).